Richard Clark is an InduSoft Web Studio application developer at Wonderware by Schneider Electric. Clark has been an application developer and professional technical writer for more than 15 years at InduSoft. Contact him at [email protected].
Hardware devices designed specifically for hosting HMIs, whether wired or wireless, are now using built-in chip sets that employ specific secure connectivity protocols such as OPC-UA. These protocols make the hardware devices safe in a wired or wireless enterprise when collecting data and when runtime components exist as cloud-based services.
Standard Ethernet interfaces and Internet connections can be used for securely distributing this collected data to remote users and condition monitoring systems, and modern HMIs make these communications easy to establish with support for OPC and other data schema standards.
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HMIs need to connect to two main types of devices to collect the plant operating data used for condition monitoring: controllers and smart field devices. Connections to PLCs, motor controllers, and other similar components are generally made via Ethernet, though older controllers may require serial or other proprietary connections (see Figure 1).
Whether the HMI is hosted on a PC or an embedded platform such as Windows Embedded or Linux, it will most likely have an Ethernet port that can connect to many controllers and support multiple protocols through this single connection. Popular Ethernet protocols that modern HMIs support include EtherNet/IP, Modbus TCP, and Profinet.
For serial connections, RS-232 and RS-422/485 connections are common; hundreds of protocols are in use. Many modern HMIs will support more than 200 protocols. For unsupported protocols, end users can write custom drivers.
Smart field devices can be smart instruments, pneumatic valve manifolds, or other types of devices. A device is defined as smart if it supports a digital communications protocol. Common smart field-device communication protocols include DeviceNet, Foundation Fieldbus, and Profibus DP and PA. Modern HMIs will have support for these protocols built in, easing connectivity. Often, the best way to distribute plant data to users is via the cloud, following these steps:
- Choose a cloud service provider
- Select an HMI with built-in cloud support
- Connect the HMI to the cloud
- Establish secure access for remote and local devices.